Posted by **ramana** on Wednesday, June 18, 2008 at 3:36pm.

what rate willl an amount double itself in 20 years at simple interest?

- 10th -
**DrBob222**, Wednesday, June 18, 2008 at 3:59pm
(1.00+x)^20 = 2 where x is the percent. If we call 1.00 + x = Y, then

(Y)^20 = 2

20*log(Y) = log 2

20*log(Y) = 0.30103

log Y = 0.30103/2 =

Solve for y and that will tell you what 1+interest rate must be. Subtracting 1.00 will give you the interest rate. I get something like 3.5%

- 10th -
**Damon**, Wednesday, June 18, 2008 at 4:04pm
In 20 years you must make one times the original amount in interest.

20 x = 1

x = .05 or 5%

- 10th -
**Damon**, Wednesday, June 18, 2008 at 4:05pm
It said simple, not compound.

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